linux-kernel - Re: [PATCH 2/2] OPP: Call dev_pm_opp_set

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Message-ID: <20231025073634.4et5epfog25o2pxf@vireshk-i7>
Date:   Wed, 25 Oct 2023 13:06:34 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stephan Gerhold <stephan.gerhold@...nkonzept.com>
Cc:     Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] OPP: Call dev_pm_opp_set_opp() for required OPPs

Thanks a lot for taking this up, really appreciate it Stephan.

On 24-10-23, 13:18, Stephan Gerhold wrote:
> Unfortunately this patch breaks scaling the performance state of the
> virtual genpd devices completely. As far as I can tell it just keeps
> setting level = 0 for every OPP switch (this is on MSM8909 with [1],
> a single "perf" power domain attached to the CPU):
> 
> [  457.252255] cpu cpu0: _set_opp: switching OPP: Freq 998400000 -> 799999804 Hz, Level 0 -> 0, Bw 3200000 -> 1600000
> [  457.253739] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 998400000 -> 799999804 Hz, Level 0 -> 0, Bw 3200000 -> 1600000

The thing I was more worried about worked fine it seems (recursively calling
dev_pm_opp_set_opp() i.e.).

> [  457.304581] cpu cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000
> [  457.306091] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000
> [  457.323489] cpu cpu0: _set_opp: switching OPP: Freq 533333202 -> 399999902 Hz, Level 0 -> 0, Bw 1600000 -> 800000
> [  457.352792] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 533333202 -> 399999902 Hz, Level 0 -> 0, Bw 1600000 -> 800000
> [  457.353056] cpu cpu0: _set_opp: switching OPP: Freq 399999902 -> 199999951 Hz, Level 0 -> 0, Bw 800000 -> 800000
> [  457.355285] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 399999902 -> 199999951 Hz, Level 0 -> 0, Bw 800000 -> 800000
> 
> Where do you handle setting the pstate specified in the "required-opps"
> of the OPP table with this patch? I've looked at your changes for some
> time but must admit I haven't really understood how it is supposed to
> work. :-)

Thanks for the debug print, they helped me find the issue.

> [  457.304581] cpu cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000
> [  457.306091] genpd genpd:1:cpu0: _set_opp: switching OPP: Freq 799999804 -> 533333202 Hz, Level 0 -> 0, Bw 1600000 -> 1600000

The second line shouldn't have had freq/bw/etc, but just level. Hopefully this
will fix it. Pushed to my branch too. Thanks. Please try again.

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 056b51abc501..cb2b353129c6 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1070,7 +1070,7 @@ static int _set_required_opps(struct device *dev, struct opp_table *opp_table,

        while (index != target) {
                if (devs[index]) {
-                       ret = dev_pm_opp_set_opp(devs[index], opp);
+                       ret = dev_pm_opp_set_opp(devs[index], opp->required_opps[index]);
                        if (ret)
                                return ret;
                }

-- 
viresh